As a method for measuring the surface shape of a measurement object, there is a method that, using illumination light such as laser light or the like, images the reflected light of illumination light from the measurement object and thereby measures the surface shape of the measurement object.
For example, Patent Literature 1 discloses a technology that measures the surface shape of a strip-shaped body such as a moving steel plate as a measurement object on the basis of the principle of light section. In Patent Literature 1, the reflected light of linear light applied along the width direction of the measurement object is imaged by an area camera, and the surface unevenness information of the measurement object is acquired from the amount of displacement of the imaged reflected light of the linear light (that is, the light section line).